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ISO 28564-4: Location Identification — Part 4: Emergency Exits
Design, performance, and installation requirements for emergency exit signage
1. Purpose and Scope of ISO 28564-4
ISO 28564-4 specifies the design, performance, and installation requirements for emergency exit signage used in buildings, underground structures, transportation vehicles, and maritime vessels. As the fourth part of the location identification series, this standard focuses specifically on exit signs that guide occupants to safety during fire, power failure, smoke conditions, or other emergency events. The standard consolidates requirements from ISO 16069 (safety way guidance systems) and ISO 7010 (safety signs) into a unified emergency exit sign specification with quantified photometric and geometric performance criteria.
Emergency exit signs specified per ISO 28564-4 should use the “running man” pictogram (ISO 7010-E002) rather than text-only signs. Studies demonstrate that the pictogram is recognised 3–5 times faster under simulated smoke conditions compared to文字-based signs, regardless of the observer’s native language.
| Performance Parameter | Standard Requirement | Enhanced (High-Risk Occupancy) |
|---|---|---|
| Minimum luminance (electrically powered) | 50 cd/m² | 100–300 cd/m² |
| Luminance uniformity (max/min ratio) | 10:1 | 5:1 |
| Minimum operating duration (battery backup) | 60 minutes | 180 minutes |
| Charging time to 100 % capacity | ≤ 24 hours | ≤ 12 hours |
| Visibility distance (clear conditions) | 30 m | 45 m (for signs ≥ 300 mm height) |
| Smoke penetration contrast | ≥ 0.3 (modulated contrast) | ≥ 0.5 |
2. Photometric Performance and Visibility
The photometric requirements in ISO 28564-4 address both normal operation (mains-powered) and emergency operation (battery-backed or photoluminescent). For electrically powered signs, the minimum surface luminance of 50 cd/m² ensures visibility under daylight conditions up to 30 m viewing distance. However, the standard also introduces a novel requirement: modulated contrast under simulated smoke conditions. This test, defined in ISO 28564-4 §7.3, measures the sign’s ability to remain legible when the observer is viewing through a controlled smoke aerosol with optical density of 0.15 m&supminus;1 (equivalent to light transmission of approximately 70 % per metre).
A common design error is assuming higher luminance always equals better visibility in smoke. Above 500 cd/m², scattered light from smoke particles creates a veiling luminance that actually reduces perceived contrast. The optimal luminance for smoke-penetrating exit signs is 100–300 cd/m², not the maximum achievable.
Edge-lit LED exit signs have largely replaced traditional incandescent and fluorescent signs due to superior energy efficiency (2–5 W versus 15–40 W for incandescent) and longer service life (50,000–100,000 hours LED versus 2,000–8,000 hours for incandescent). However, thermal management is critical: LED junction temperature must remain below 85 °C to prevent accelerated lumen depreciation. Signs installed near HVAC ducts or heat sources require derating calculations per the LED manufacturer’s specifications.
3. Installation and Compliance Engineering
The standard specifies mounting height, spacing, and placement relative to exit doors and corridors. Every exit door must have a sign directly above or adjacent to it (within 1 m horizontally), and directional exit signs must be placed at intervals not exceeding 15 m along escape routes and at every change of direction. In open-plan areas, the maximum distance to the nearest visible exit sign is 30 m.
- Photoluminescent signs: These signs, charged by ambient light (minimum 50 lx at the sign surface for 60 minutes), must maintain ≥ 8 cd/m² for 60 minutes after lights-out. Strontium aluminate pigments (type II per ISO 17398) are the de facto standard. Recharge time after full discharge is typically 4–8 hours under standard office lighting conditions.
- Battery backup systems: Central battery systems (48 V DC) serving multiple signs offer lower lifetime cost per sign compared to individual self-contained battery packs, but require fire-rated cable routing (minimum 30 minutes fire resistance per IEC 60331). Self-contained signs simplify installation but require annual battery replacement and individual monitoring.
For facilities with complex evacuation plans, integrating ISO 28564-4 exit signage with a building management system (BMS) allows dynamic reconfiguration of exit routes. During a fire on the east wing, the BMS can activate strobe-equipped signs directing occupants away from the affected zone while maintaining compliance with the static sign placement requirements.
In parking garages and semi-enclosed structures, standard exit signs rated for indoor use only (IP20) will fail within 6–12 months due to moisture ingress and corrosive vehicle exhaust condensate. Always specify minimum IP54 rated signage for these environments, with stainless steel or UV-stabilised polycarbonate housings.
4. Frequently Asked Questions
Q: Can photoluminescent exit signs replace electrically powered signs in all occupancies?
A: Many building codes permit photoluminescent signs only in occupancies where the evacuation time is less than 60 seconds (e.g., single-storey retail). High-rise buildings, healthcare facilities, and assembly occupancies with long egress paths generally require electrically powered signs with battery backup to ensure visibility throughout the entire evacuation period.
A: Many building codes permit photoluminescent signs only in occupancies where the evacuation time is less than 60 seconds (e.g., single-storey retail). High-rise buildings, healthcare facilities, and assembly occupancies with long egress paths generally require electrically powered signs with battery backup to ensure visibility throughout the entire evacuation period.
Q: How often should emergency exit signs be tested?
A: ISO 28564-4 recommends monthly functional testing (30-second battery-only operation) and annual full-duration testing (90–180 minutes depending on occupancy classification). Records of all tests must be maintained for a minimum of 3 years.
A: ISO 28564-4 recommends monthly functional testing (30-second battery-only operation) and annual full-duration testing (90–180 minutes depending on occupancy classification). Records of all tests must be maintained for a minimum of 3 years.
Q: Does the standard address wayfinding for people with visual impairments?
A: Yes. ISO 28564-4 §8.5 requires tactile indicators on exit signs at a height of 900–1100 mm, audible evacuation signals, and in larger facilities, voice evacuation systems that provide directional guidance via ceiling-mounted speakers.
A: Yes. ISO 28564-4 §8.5 requires tactile indicators on exit signs at a height of 900–1100 mm, audible evacuation signals, and in larger facilities, voice evacuation systems that provide directional guidance via ceiling-mounted speakers.
Q: Are there special requirements for exit signs in cold storage or freezer environments?
A: Yes. Signs in low-temperature environments (−20 °C or below) require cold-rated LED drivers (rated for −40 °C minimum) and heated sign faces to prevent ice formation that can obscure the pictogram. Standard lithium-based battery backup systems must be replaced with nickel-cadmium or specialty low-temperature chemistries.
A: Yes. Signs in low-temperature environments (−20 °C or below) require cold-rated LED drivers (rated for −40 °C minimum) and heated sign faces to prevent ice formation that can obscure the pictogram. Standard lithium-based battery backup systems must be replaced with nickel-cadmium or specialty low-temperature chemistries.
